The present invention relates to processing of video signals, and more particularly to a histogram-based segmentation of an image or video signal into visual objects via color moments.
In the processing of images or video signals it is desirable to be able to take an object, such as a tennis player, from one video signal or image and superimpose it upon another video signal or image. To this end keying systems were developedxe2x80x94either luminance or chrominance based. For example, in character generation luminance keying is typically used, while chrominance keying is used for placing a weather man in front of a weather map. Chrominance keying is based upon the object to be segmented, i.e., the weather man, being situated before a uniform color background, such as a blue screen. A key signal is generated that is one value when the color is blue and another value when the color is not blue. The key signal is then used to cut a hole in another video signal into which the segmented object is placed, thus superimposing an object from one video signal onto another.
In naturally occurring scenes there may be many objects against a non-uniform color background, such as tennis players and the ball against a crowd background. It may be desirable to segment an object from this scene in order to superimpose it upon another scene. In this situation conventional luminance and chrominance key generation techniques do not work.
What is desired is a method of segmenting an object from an image in a video signal using the colors of the object.
Accordingly the present invention provides histogram-based segmentation of an image or video signal into objects via color moments. A user defines a relatively large area that lies entirely within an object of interest in one image, frame or picture from the video signal. An algorithm extracts characteristics of the user-defined area. Using these characteristics the algorithm grows the area to encompass the entire object of interest. The characterization of the area is made based on its color properties. Color moments representing a color histogram for the area are used for characterizing the color properties. Weighting factors and a threshold are automatically calculated for use in the characterization. At the conclusion the xe2x80x9ccharacteristicxe2x80x9d color moments for the object are updated.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.